The sphere spark gap

The limitations of the present needle point spark gap are discussed and the use of a spark gap having two equal spheres is proposed. The space required by a vertical sphere gap having the lower sphere grounded is very much less than that required by a needle point gap for the same voltage range. Corona and resultant inconsistencies are prevented if the spheres are used over a separation not greater than their diameter. This leads to large spheres for high voltages. Sphere gaps have proved satisfactory in commercial, testing because they are reliable, more convenient, require less floor space, and are portable. Spheres of 25 cm., 37½ cm., and 50 cm. diameter covering ranges of approximately 50,000 to 275,000; 50,000 to 412,500 and 50,000 to 550,000 volts effective values, respectively, are proposed as standards. A few features are suggested to be incorporated in the Standardization Rules.